[patch for-3.14] mm, mempolicy: fix mempolicy printing in numa_maps

[David Rientjes <rientjes@google.com>]

As a result of commit 5606e3877ad8 ("mm: numa: Migrate on reference 
policy"), /proc/<pid>/numa_maps prints the mempolicy for any <pid> as 
"prefer:N" for the local node, N, of the process reading the file.

This should only be printed when the mempolicy of <pid> is MPOL_PREFERRED 
for node N.

If the process is actually only using the default mempolicy for local node 
allocation, make sure "default" is printed as expected.

Reported-by: Robert Lippert <rlippert@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 This affects all 3.7+ kernels and is intended for stable but will need to
 be rebased after it's merged since mpol_to_str() has subsequently
 changed.  I'll rebase and propose it separately.

 mm/mempolicy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2926,7 +2926,7 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
 	unsigned short mode = MPOL_DEFAULT;
 	unsigned short flags = 0;
 
-	if (pol && pol != &default_policy) {
+	if (pol && pol != &default_policy && !(pol->flags & MPOL_F_MORON)) {
 		mode = pol->mode;
 		flags = pol->flags;
 	}

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